516 BEACHIOPODA. 



organs. The blood which circulates through them will consequently 

 be returned in a perfectly aerated condition, to be mixed, however, with 

 that in a less pure state from the visceral lacunes, before it enters the 

 heart. This mixed state of the blood is not by any means peculiar to 

 these animals ; for it obtains in many of even the higher Mollusks. 



(1356.) Nervous system. As in all true Mollusks, the ganglionic 

 centres are placed in connexion with a nervous collar surrounding the 

 03sophagus. In Waldheimia australis the collar is situated at the com- 

 mencement of the alimentary tube ; and there are five nervous centres, 

 three of which, on account of their superior size, may be assumed to be 

 the principal oesophageal ganglia, from which nerves are given off to 

 supply the pallial apparatus, the muscles, and the various viscera of the 

 body. 



(1357.) No special organs of sense have yet been observed ; indeed, 

 sight, hearing, or smell could be of little use to animals like the Bra- 

 chiopods, deprived of locomotion, and firmly fixed during the whole 

 period of their lives to one spot. Forbes and Hanley, in their < British 

 Mollusca,' regard as ocelli and otolitic capsules certain red spots, per- 

 ceptible in some species at the bases of the setigerous follicles ; but 

 these Mr. Hancock thinks are nothing more than glandular matter in 

 connexion with the growth of the setae. 



(1358.) The Reproductive system of the Brachiopoda has been minutely 

 described by Mr. Albany Hancock in the memoir above quoted. In 

 Waldheimia australis the generative organs consist of thick bands some- 

 what convoluted and ramified ; they are of a full yellow colour, and are 

 lodged in the trunks and main branches of the great pallial sinuses. 

 There are four of these bands, two in each lobe : those in the dorsal lobe 

 are single, and occupy the two outer or lateral sinuses, extending from 

 behind the attachment of the occlusor muscles to within a short distance 

 of the anterior margin of the mantle ;. their posterior extremities reach 

 to the perivisceral chamber. The ventral pair extend as far forward as 

 the dorsal, and are double, that is, each forms a loop, the free extre- 

 mities of which pass into the outer and inner sinuses of the same side ; 

 the looped portions lie within the perivisceral chamber. These genital 

 bands are attached to the inner lamina of the mantle throughout their 

 whole extent by a membrane which, originating in this lamina, passes 

 into a groove extending along the under surface of the genital band. 

 The genital or pallial artery runs along the edge of this membrane, and 

 has the reproductive organ developed around it. This is the most 

 obvious disposition of the parts, as apparent on a general examination ; 

 but on a closer inspection, there can be but little doubt that these 

 organs are in reality developed between the two membranes which com- 

 pose the inner lamina of the mantle, and, bulging out the interior of 

 these, become suspended, as it were, in the pallial sinus. Those in 

 which ova are deficient are generally supposed to be the male secreting 



